One method for assessing the potential oil recovery from existing boreholes, involves the drilling of side holes from locations within the borehole, so that a fluid injector can be placed within one side hole and a fluid detector placed within another nearby side hole to measure the flow of a tracer fluid between them through the strata. My earlier patent application Ser. No. 903,240, filed May 5, 1978 on Side Hole Drilling in Boreholes, describes a technique for drilling such side holes. Due to the narrow confines of the bore hole, it is difficult not only to drill the side holes, but also to properly install the probes. An assessment apparatus that minimized the time and equipment required in the borehole, would facilitate the use of side hole probe geologicaL assessment techniques.